A WLAN (Wireless Local Area Network, wireless local area network) is a computer local area network that uses a radio channel as a transmission medium, and is an important supplement and extension to a wired network. The basic network structure of the WLAN includes three network devices: station (STA, Station), access point (AP, Access Point), and access control point (AC, Access Control).
The function of the AP is to connect the stations to the existing wired network. With the constant application of the WLAN technology, more and more APs are deployed in the network. The version upgrade and the configuration management of the APs result in a high operating expenditure of an operator. To reduce the operating expenditure of the network, the operator expects to control and manage APs through the access control point AC in a centralized way, which gives rise to a WLAN network of thin APs.
A tunnel is set up between the thin AP and the AC through a CAPWAP (Control And Provisioning of Wireless Access Point, control and provisioning of wireless access point) protocol, and the AC manages thin APs through the CAPWAP protocol. Data is transmitted between the WLAN station STA and the thin AP through 802.11 frames. The thin AP converts the 802.11 frames of the WLAN station STA into a frame format identifiable by the AC, and sends them to the AC.
FIG. 1 is a sequence chart of a thin AP implementing WLAN user access. Referring to FIG. 1, the CAPWAP link between the AP and the AC provides normal communication through the steps such as (1) capwap_discovery and (2) capwap_configuration; the WLAN station STA sends an association request (association_req) frame to the thin AP, and the thin AP sends a capwap_req_association message to the AC, requesting the AC to confirm whether the WLAN station is allowed to be associated; the AC makes a determination, and delivers a capwap_resp_association message to the AP if the association is allowed, and the AP sends an association response (association_resp) frame to the WLAN station to indicate that the association is allowed, which means that a wireless link is set up successfully between the WLAN station and the AP. Afterward, the WLAN station can start access authentication. After the authentication is passed, the WLAN station can start to play a video on demand. The multicast service is an important content of carrying out the WLAN service. The multicast service rights control is a primary breakthrough point for the operator to deploy the multicast service of the WLAN network. To obtain the multicast data in a video-on-demand process, the WLAN station needs to obtain the play on-demand rights first.
While the WLAN station plays a multicast video on demand in the prior art, the AP transmits the IGMP (Internet Group Management Protocol, Internet Group Management Protocol) request message of each WLAN station to the AC transparently. After receiving the IGMP request message, the AC determines the multicast program rights of the WLAN station according to a preset multicast control policy. If the WLAN station is allowed to play the multicast program, the AC replicates a multicast stream for the WLAN station, and forwards the multicast stream to the WLAN station through the AP. The destination MAC (Media Access Control, media access control) address of the multicast stream is the MAC address of the WLAN station, and the destination IP address of the multicast stream is the IP address of a multicast group. After receiving the multicast program stream, the AP uses the pre-agreed multicast key to encrypt the multicast program stream and then sends the multicast program stream to the WLAN station.
FIG. 2 is a schematic diagram of an on-demand multicast process of a WLAN station in the prior art. Referring to FIG. 2, in the process of implementing the present disclosure, the inventor finds that because the AC is responsible for multicast rights control, the AP forwards the IGMP REPORT (report) message to the AC directly after receiving the message from the WLAN station, and the AC decides whether to allow the WLAN station to play the specified multicast stream on demand according to a preset multicast control policy. The AC replicates a multicast stream for each permitted WLAN station. The technical solution in the prior art causes the following problems: the multicast replication node of the WLAN station is the AC device, which leads to serious waste of downlink bandwidths and too heavy multicast replication pressure on the AC device; the multicast control node of the WLAN station is the AC device, which leads to too centralized loads on the AC device; every IGMP protocol message of the WLAN station is forwarded by the AP to the AC, which leads to waste of some uplink bandwidths.